Blackfin Tuna Research Articles

Bioaccumulation potentials of per-and polyfluoroalkyl substances (PFAS) in recreational fisheries: Occurrence, health risk assessment and oxidative stress biomarkers in coastal Biscayne Bay

Per-and polyfluoroalkyl substances (PFAS) are a group of synthetic, highly fluorinated, and emerging chemicals that are reported to be used for both industrial and domestic applications. Several PFAS have demonstrated persistent, bioaccumulative and toxic tendencies in marine organisms. Therefore, this research aims to characterize and quantify these compounds in both recreational fisheries and surface water samples, including estimating their bioaccumulation potentials. In addition, we assessed the potential contribution of biomonitoring tools such as oxidative stressors and morphological index on fish and ecological health. Finally, human health risk assessment was performed based on available toxicological data on limited PFAS. All PFAS were detected in at least one sample except for N-EtFOSAA in lobster which was below the method detection limit. ƩPFAS body burden ranged from 0.15 to 3.40 ng/g wet weight (ww) in blackfin tuna samples and 0.37–5.15 ng/g ww in lobster samples, respectively. Wilcoxon rank paired test (α = 0.05) shows that there is statistical significance (ρ < 0.05) of ƩPFAS between species. Bioaccumulation factors (BAF) suggest an increasing trend in PFAS classes (PFCAs < PFSAs < FTSs), with higher BAFs observed in tuna compared to lobster. Long-chain PFESAs and FASAA were reported at higher concentrations in lobster compared to Blackfin tuna due to their bioavailability through sediment-sorption interactions. Although Fulton’s condition factor (FCF) indicates healthy fish conditions, oxidative stress biomarkers suggest that tuna and lobster might be under stress, which can weaken their immune system against exposure to emerging contaminants such as PFAS. Hazard risk (HR) suggests a low risk to human health based on the consumption of the studied species; however, the risk of contaminant exposure may be higher than estimated. This study is aimed at improving food safety by providing better understanding of how PFAS infiltrate into human diet and incorporating data on influence of contaminant exposure and environmental stressors on marine health.

Age, growth, and mortality of Blackfin Tuna in the Gulf of Mexico

AbstractObjectiveAn otolith‐based aging approach was used to evaluate age and growth relationships, sexual dimorphism in growth, and derive mortality estimates for Blackfin Tuna Thunnus atlanticus in the Gulf of Mexico (GOM).MethodsBlackfin Tuna (n = 395) were sampled from recreational fisheries and aged from 0 to 13 years, representing an increase over previous estimates of longevity for the species.ResultRapid growth was exhibited during the first two years of life, and the Richards growth function provided a better fit (L∞ = 907 mm, k = 0.112 /year, a = 1.05, b = 0.25) to the data compared with the von Bertalanffy growth model (L∞ = 824 mm, k = 0.365/year, t0 = −0.96). Sexual dimorphism in growth was observed, with males (907 mm) reaching a larger L∞ than females (857 mm), and otolith mass was a strong predictor of age in both sexes. Estimated instantaneous total (Z = 0.532/year) and natural (M = 0.467 year) mortality rates for Blackfin Tuna in the GOM were low relative to previous estimates in the southwestern Atlantic, where fishing mortality (F) is likely much higher.ConclusionResults represent critical baseline estimates of size‐at‐age, longevity, and natural mortality for Blackfin Tuna at relatively low levels of exploitation that can be used to inform future assessments.

Poleward catch displacement of blackfin tuna Thunnus atlanticus in the southwestern Atlantic Ocean: Possible effect of increasing water temperatures

AbstractBlackfin tuna Thunnus atlanticus often inhabits warm waters of the western Atlantic Ocean from 40°N (Cape Cod, USA) to 22°S (Rio de Janeiro, Brazil). We recorded the first catches of the species in southern Brazil (34°S) and described its new distribution and fishing grounds. Since 2007, annual catches per trip and frequency of blackfin tuna landings increased for three oceanic fishing fleets in Southern Brazil. The spatial distribution of higher catches and the center of gravity of spatial fishing records moved poleward. Sea surface temperature anomalies for the region warmed from 1960 to 2019, and anomalies were primarily positive after 2000. Evidence suggests that the distribution of blackfin tuna moved poleward by six degrees of latitude (~660 km). The causes of this distribution extension were unclear, but ocean warming was the most likely driver.

Numerical study of a fish swimming in hydrokinetic turbine wake

The environmental effects of hydrokinetic turbines are still under investigation, reflecting the emerging status of this technology. This study investigates the interaction between hydrokinetic rotor wakes and fish swimming, revealing insights into fish biomechanics in complex flows and assessing the environmental implications of marine energy solutions. We conducted numerical simulations with the URANS approach and k−ω−SST turbulence closure model to predict three-dimensional turbulent flow in the OpenFOAM software. The hydrokinetic rotor wake was simulated employing the actuator line method, providing a computationally efficient alternative to full geometry simulations. For accurate replication of the motion of a fish-like tuna (Thunnus atlanticus), dynamic adaptive mesh discretization was employed. The results offer a comparative analysis of fish swimming performance within the wake rotor, particularly when immersed in the tip blade vortex, contrasted with scenarios where fish swim in undisturbed flow conditions. The analysis encompasses three-dimensional wake structures, force generation, efficiency, and equilibrium states (balancing drag and thrust) across varying Swimming numbers (Sw). Key findings include the enhanced attachment of the leading-edge vortex due to the caudal fin’s interaction with the tip blade vortex, resulting in improved auto-propulsive force production; a reduced tail stride frequency observed in fish swimming downstream of the rotor to achieve longitudinal force balance compared to unperturbed flow; and transverse hydrodynamic forces pushing fish radially away from the wake’s influence zone, potentially mitigating the risk of collision with turbine blades.

Assessment of the stock status of blackfin tuna Thunnus atlanticus in the Southwest Atlantic Ocean: a length-based approach

This is the first assessment of blackfin tuna Thunnus atlanticus stock status. The aim of the present study was to estimate the status of its Southwestern stock using length-based models. A total of 1929 individuals was gathered in four years of length data (1998–2019). Two length-based models were applied, Length-Based Spawning Potential Ratio (LBSPR) and Stock Synthesis Data-limited tool (SS-DL) and five scenarios combining a set of growth parameters (asymptotic length-L∞, and growth constant-K) were built to accommodate different life histories available in the literature. The natural mortality (M) was estimated through four empirical methods. Given that the fishery only selects mature fish, length at selectivity were larger than the length at first maturity and high relative fishing mortality were found at most scenarios, even with high spawning potential ratio (SPR) values. The LBSPR estimated higher values of SPR, it presented a steeper decline than SS-DL between 1998 and 2019. In addition, growth parameters influence the estimation of the virginal stock, and intermediate M/K values seems to represent better the estimated length composition, given the low historical catch of the species. A declining pattern in SPR was observed over time with a reduction of 12% according to LBSPR and 7% decrease based on SS-DL methods. However, the overall evaluation of the Southwestern Atlantic stock of blackfin tuna in 2019 revealed an SPR range of 0.41 to 0.63, suggesting sustainable exploitation. Even with the limited data, we could have a proxy of stock status estimation by using length-based models which highlights the importance of such data. However, due to the high uncertainty of the results, better collection of catch, effort and length data should be considered. Additionally, SS-DL seems to estimate better SPR values when variability of growth parameters are placed for a given species.

High throughput identification of tuna (Thunnus spp.) larvae in the Gulf of Mexico using unlabeled-probe high-resolution melting analysis (UP-HRMA).

The genus Thunnus (family Scombridae) comprises eight species of tunas of which all but one are targeted by industrialized fisheries. While intact individuals of these species can be distinguished by morphological characteristics, researchers and managers often rely on dressed, frozen, juvenile, or larval fish samples which often necessitates molecular species identification. Here we investigate short amplicon (SA) and unlabeled probe (UP) high-resolution melting analysis (HRMA) as a low-cost, high-throughput molecular genotyping assay capable of distinguishing between albacore tuna (T. alalunga), blackfin tuna (T. atlanticus), bigeye tuna (T. obesus), Atlantic bluefin tuna (T. thynnus), and yellowfin tuna (T. albacares) in the Gulf of Mexico. While SA-HRMA of variable regions in the NADH dehydrogenase subunit 4 (ND4) and subunit 5 (ND5), and subunit 6 (ND6) of the mitochondrial DNA (mtDNA) genome did yield some species-specific diagnostic melting curves (ex. ND4 assay can reliably distinguish Atlantic bluefin tuna) genotype masking produced excessive variation in melting curves for reliable multi-species identification. To minimize the genotyping masking of SA-HRMA a 26 base pair long UP containing four SNPs was developed within a 133 bp segment of ND4. The UP-HRMA is able to reliably distinguish Gulf of Mexico species T. thynnus, T. obesus, T. albacares, and T. atlanticus by UP melting temperature at 67°C, 62°C, 59°C, and 57°C respectively. The developed UP-HRMA assay is a lower-cost, higher-throughput, alternative to previously published molecular assays for tuna identification that can be easily automated for large data sets including ichthyological larval surveys, fisheries specimens lacking distinguishing morphological characteristics, or detection of fraudulent trading of tuna species.

Weak range-wide population structure in the blackfin tuna (Thunnus atlanticus) revealed by analysis of genome-wide SNPs

Abstract Blackfin tuna (Thunnus atlanticus) is a small tuna distributed in the western Atlantic Ocean where it is exploited by growing recreational and commercial regional fisheries. In this work, genome-wide genetic variation was analysed to investigate the occurrence of stock subdivision. A de novo assembly of the blackfin tuna genome was generated using Illumina paired-end sequencing data and applied as a reference for population genomic analysis of specimens from nine localities (average sample size per locality n = 72) spanning most of the blackfin tuna distribution range. A total of 2139 single-nucleotide polymorphisms were discovered and genotyped using the double-digest restriction associated DNA sequencing. Pairwise exact homogeneity tests were significant in 24 out of 36 population pairs and significant spatial autocorrelation of genotypes was observed for specimens collected within 2250 km of each other. However, divergence among locality samples was very low (pairwise FST range 0.0002–0.0025) and significant temporal variations were detected in localities sampled multiple times. Approaches to detect cryptic groups de novo were unsuccessful. Additional sampling is warranted to determine if multiple stocks need to be defined for management and assess temporal and spatial patterns of gene flow connecting them.

Climate variability and small-scale fisheries of the Albuquerque Cays Island, insular Colombian Caribbean

The relationship between climate variability and the small-scale fishery (SSF) of the Albuquerque Cays was studied from 2004 to 2018. The environmental variables analyzed were: sea surface temperature (SST), wind magnitude, and chlorophyll (Chl-α). The fishery is multi-species; 410 individuals were identified, belonging to 4 orders, 15 families, and 62 species, of which 38.7% are reef, 35.5% demersal, and 25.8% pelagic. The most dominant species were Caranx latus, Elagatis bipinnulata, Coryphaena hippurus, Lutjanus vivanus, Ocyurus chrysurus, Thunnus atlanticus, Sphyraena barracuda, Canthidermis sufflamen, Etelis oculatus, Acanthocybium solandri, Lutjanus jocu, Balistes vetula, Lutjanus buccanella, followed by Rhomboplites aurorubens and Mycteroperca bonaci. The pelagic species that contribute the most in biomass and commercial importance are S. barracuda, A. solandri, T. atlanticus, and E. bipinnulata, the most important due to their high market value. A significant correlation was found among SST, Chl-α, wind magnitude, and catch per unit effort (CPUE) anomalies. The highest CPUE values occurred in January, March, June and September were associated with the passage of cold fronts and hurricanes, giving way to new fishing opportunities and conservation of some resources.

Population structure of blackfin tuna (Thunnus atlanticus) in the western Atlantic Ocean inferred from microsatellite loci

The blackfin tuna, Thunnus atlanticus, is a small tropical tuna exploited by recreational and commercial fisheries in various parts of its range. Information on stock structure is needed to develop management plans for this species but is currently lacking. In this work, 470 blackfin tuna from nine geographic populations were assayed at 13 homologous microsatellite markers to provide a first assessment of stock structure across the species range. The overall divergence among locality samples was very low (overall FST = 0.0004) indicating high connectivity of blackfin tuna across their range. No clear grouping of localities in differentiated units was inferred but structuring followed a weak isolation by distance pattern (r = 0.16, P = 0.032). Pairwise exact tests and spatial analysis of molecular variance suggested divergence of the sample collected offshore Baía Formosa (Brazil) possibly reflecting reproductive isolation of Brazilian populations from those in the Caribbean region and further north. Further study of the status of Brazilian populations and the transition between this region and the Caribbean is warranted. Cryptic subdivision within the Northern Hemisphere part of the range is possible and should be evaluated using increased marker density and a more comprehensive geographic coverage.

Stable Isotopic Niche Variability and Overlap across Four Fish Guilds in the North‐Central Gulf of Mexico

AbstractThe quantification of niche diversity and niche overlap is useful for understanding the impacts of fisheries regulation and management. In this work, we evaluate isotopic niche size and overlap at the guild and species levels. Specifically, we analyzed guild‐ and species‐specific isotopic niche space and niche space overlap using the SIBER and nicheROVER packages, and we evaluated length‐specific and geographic contrasts in isotopes for fishes in the north‐central Gulf of Mexico. Stable carbon and nitrogen isotope values (δ13C and δ15N) of fish species were compared among four ecotype‐based fish guilds: estuarine, coastal migratory pelagic (CMP), reef, and large offshore pelagic (LOP). Significant differences in the mean stable isotope values were found among fish guilds. Estuarine guild species exhibited the highest δ13C variability, and Red Drum Sciaenops ocellatus were the most isotopically diverse. Variability of δ13C for CMP fish was comparable to that of some estuarine species, whereas reef and LOP fish were less variable. Fishes within the LOP guild had the largest δ15N range. Reef guild fishes had the smallest isotopic niche space and LOP guild species consistently had the largest, although no species in any guild occupied as large of an isotopic niche space as Red Drum. Distinct and well‐separated isotopic niches were also observed between most estuarine species and CMP species; however, high niche overlap was observed for species within the reef and LOP guilds. We found a positive relationship of δ15N and fish TL for Red Drum, Blackfin Tuna Thunnus atlanticus, and Yellowfin Tuna T. albacares, and we found that δ15N values for Red Drum and Red Snapper Lutjanus campechanus showed distinct isotope differences between geographic areas. This study provides data not only on how species within and without ecotypes interact but also on the variability of their interactions, all of which can inform ecosystem‐based fisheries management models.

Some like it hot, hungry tunas do not! Implications of temperature and plankton food web dynamics on growth and diet of tropical tuna larvae

Abstract Restricted to low-productivity environments near their thermal maxima, larval tunas may be threatened by warming global temperatures, yet our understanding of how they are constrained is limited. We examined blackfin tuna (Thunnus atlanticus, presumptive) diet and growth in the context of their prey and predators in the Straits of Florida in 2 years with contrasting summer conditions: low temperature (26.7–28.3°C)–high prey and high temperature (28.4–29.0°C)–low prey. In the cooler, high-prey conditions, larvae had 30% faster growth (0.45 mm d−1), fuller guts from predominantly feeding on calanoid copepods, and were 10× more abundant, dominating the larval fish assemblage. In contrast, in warm, low-prey conditions fewer, younger, and slower-growing (0.35 mm d−1) T. atlanticus fed predominantly on nauplii and had less full guts. Modelling individual growth across years revealed that growth peaked at an optimum of 28.5°C (5°C below known thermal maxima in the field) and high densities of predators selectively consumed slower-growing larvae. Low-prey availability may reduce the thermal optima of larvae, as growth and survival are diminished when low prey and high temperature coincide. Our results illustrate the importance of considering food web dynamics with temperature when predicting the response of organisms to ecosystem variability, particularly ongoing climate change.

Three-dimensional viscous wake flow in fish swimming - A CFD study

In the present paper, the assessment of the hydrodynamics of fish swimming wake-flow is carried out to identify the main features related to the propulsion performance. Two different fish models with caragiform kinematics are studied: tuna fish (Thunnus atlanticus) and lambari (Astyanax bimaculatus). CFD methods were used to simulate laminar and turbulent flow regimes and a dynamically adaptive mesh discretization (ALE) was employed to reproduce fish motion. Simulations were run in a typical range of Reynolds (Re) and Strouhal (St) numbers of the fish swimming flow investigating hydrodynamics forces and the flow patterns of the induced fish-swimming wake. Firstly, equilibrium condition (drag balancing thrust) for Strouhal was achieved for each Reynolds number and three-dimensional wake structures were evaluated concluding that fish swimming experiencing a forward locomotion movement with a reversal von-Kármán vortex street and a high-velocity jet through the downstream direction. Finally, vorticity dynamics analysis showing that the leading-edge vortex produced by the caudal fin is associated to the peak of thrust in the motion cycle.

Pelagic Habitat Partitioning of Late-Larval and Juvenile Tunas in the Oceanic Gulf of Mexico

Tunas are ecologically important in pelagic ecosystems, but due to their high economic value, large-bodied species are overfished. Declines in fishery landings of large-bodied tuna species in the Gulf of Mexico (GoM) are expected to increase fishing pressures on unmanaged, small-bodied tuna species, whose life history traits are less known. While predicting spawning stocks and recruitment success typically focuses on estimates of larval abundances, juveniles may provide a better estimate of future adult stock sizes, as they are more likely to survive to adulthood because mortality rates scale inversely with body size. However, distributional studies on juveniles are rare, leading to a gap in our understanding of tuna ecology. In the present study, tuna early life stages were collected across the GoM from January-September 2011. The size class examined in this study, representing large larvae and small juveniles, is larger than that of previous larval tuna studies in the GoM. Faunal composition, abundance, frequency of occurrence, and diel catchability were investigated. Generalized additive models (GAMs) were used to examine spatiotemporal distributions of the family Scombridae and the three most-abundant tuna species in the GoM’s epipelagic waters with respect to location, oceanographic features, and temporal change. In total, 11 of the 16 scombrid species inhabiting the GoM were collected, with small-bodied tuna species (Euthynnus alletteratus, Thunnus atlanticus, Auxis thazard) dominating the assemblage. Overall, scombrids were caught at higher abundances and frequencies at night than during the day, demonstrating that nighttime sampling generates a more accurate representation of faunal abundance and distribution. Abundance and presence-absence GAMs identified a coastal group (E. alletteratus and A. thazard) associated with productive continental shelf/slope environments (low salinity, higher chlorophyll a concentrations, nearer to shelf break) and an oceanic group (represented by T. atlanticus) associated with offshore, oligotrophic habitats (high salinity, lower chlorophyll a concentrations, further from shelf break). These results demonstrate that over a broad spatiotemporal domain, large larvae and juvenile tunas partition pelagic habitat on the mesoscale in addition to the temporal partitioning of adult spawning. These factors are important for spatially and temporally explicit modeling aimed at predicting tuna stock sizes.

Aggregative capacity of experimental anchored Fish Aggregating Devices (aFADs) in Northeastern Brazil revealed through electronic tagging data

Abstract Catches of pelagic fish associated to anchored Fish Aggregating Devices have been responsible for increases in income, fish consumption, and even cultural identity of artisanal fishing communities in many developing countries worldwide. Nonetheless, in Brazil, aFAD fishing is still poorly developed and studied. In this experiment, FADs were anchored offshore the city of Recife (Northeastern Brazil) to investigate the potential of moored buoys in the aggregation of commercially important pelagic species near the coast, as an alternative fishing site for artisanal fishers. The behavior of acoustically tagged fish was investigated to assess whether they were attracted to the FADs and how long they remained associated to them. The results indicated that, although economically important species were found near the FADs, they did not remain associated for long periods. From the four species tagged, Acanthocybium solandri, Coryphaena hippurus, Thunnus atlanticus, and Caranx crysos, only the two latter were detected at the FADs. Both species presented a preference for a specific FAD, with stronger site fidelity being recorded for C. crysos. This species presented Total Resident Times (TRTs) of more than a month and continuous residence times of more than 14 consecutive days. T. atlanticus, on the other hand, remained around the buoys for short time intervals, with a maximum TRT of only two days. Short diurnal excursions far from the FADs and few longer excursions during nighttime were recorded for C. crysos. These results do not support the possible use of moored FADs near the coast of Recife as an alternative fishing site for artisanal fisheries. It is possible that the geomorphological characteristics of the experimental area did not favor the aggregative behavior of large pelagic fish species, such as tunas, around FADs.

Tracking mercury in the southwestern Atlantic Ocean: the use of tuna and tuna-like species as indicators of bioavailability.

Mercury is a trace element that is potentially dangerous due its high toxicity and tendency to bioaccumulate in organisms. Currently, high mercury concentrations are seen in the environment especially due climate changes. Studies regarding mercury bioavailability in the southwestern Atlantic Ocean using tuna and tuna-like species are rare. The aim of the present study was to use tuna and tuna-like species (Thunnus atlanticus, Thunnus albacares, Katsuwonus pelamis, Euthynnus alletteratus, Coryphaena hippurus and Sarda sarda) as indicators of the availability of total mercury (THg) in oceanic food webs of the southwestern Atlantic Ocean. THg concentrations varied significantly among species for both muscle and liver (Kruskal-Wallis test; H5,130 = 52.7; p < 0.05; H5,130 = 50.1; p < 0.05, respectively). The lowest concentrations were found in C. hippurus (0.008mgkg-1 wet weight in the muscle and 0.003mgkg-1 wet weight in the liver), and the highest concentrations were reported in the muscle of T. atlanticus (1.3mgkg-1 wet weight) and in the liver of S. sarda (2.5mgkg-1 wet weight). The continued monitoring of tuna and tuna-like species is necessary to assist in their conservation since tuna can be sentinels of mercury pollution.

Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 631:181-199 (2019) - DOI: https://doi.org/10.3354/meps13126 Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation Stephen J. Poland1,2, Frederick S. Scharf1,*, Michelle D. Staudinger1,3 1Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 S. College Road, Wilmington, NC 28403, USA 2North Carolina Division of Marine Fisheries, 3441 Arendell St., Morehead City, NC 28557, USA 3DOI Northeast Climate Adaptation Science Center, Morrill Science Center, 611 North Pleasant Street, University of Massachusetts, Amherst, MA 01003, USA *Corresponding author: scharff@uncw.edu ABSTRACT: Sustainable management of marine fishery resources requires an understanding of the ecological relationships that contribute to community structure and population dynamics. In offshore marine ecosystems, the functional roles played by many large pelagic predators are poorly understood, yet this knowledge is essential to ecosystem-based management approaches. Here we report on the results of a multiyear (2010-2013) study to evaluate the trophic relationships within a guild of apex predatory fishes in the western Atlantic Ocean. Quantitative diet analyses were completed for wahoo Acanthocybium solandri, dolphinfish Coryphaena hippurus, yellowfin tuna Thunnus albacares, and blackfin tuna T. atlanticus during multiple seasons. Fishes were the most important prey by mass for all predators during all seasons and occurred with high frequency; however, crustacean and molluscan prey were also important dietary components for most of the predators. The diversity of prey eaten was high, with nearly 50 unique families represented; yet, a few prey groups such as scombrid fishes (Auxis spp.), flying fish (exocoetids), and ommastrephid squids, occurred more universally and dominated the diets of some predators during certain seasons. Diet similarity was highest between dolphinfish and blackfin tuna and also between wahoo and yellowfin tuna, but was generally dependent on season and driven by overlap in fish prey. Importantly, the extent of piscivory and specialization on unique fish prey groups supported a structured piscivore guild within this pelagic ecosystem, leading to separation among trophic niches and reduced overlap in prey resources. Our findings provide a temporally (seasonal and inter-annual) extensive evaluation of the trophic relationships among large pelagic fish predators in the US South Atlantic, which should inform an ecosystem-based understanding of community dynamics and fishery impacts. KEY WORDS: Blackfin tuna · Yellowfin tuna · Wahoo · Dolphinfish · Trophic interactions · Predator-prey · Food habits · Trophic niche Full text in pdf format Supplementary material PreviousNextCite this article as: Poland SJ, Scharf FS, Staudinger MD (2019) Foraging ecology of large pelagic fishes in the US South Atlantic: structured piscivory shapes trophic niche variation. Mar Ecol Prog Ser 631:181-199. https://doi.org/10.3354/meps13126 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 631. Online publication date: November 21, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

CARACTERIZAÇÃO DE UMA PESCARIA DE PEQUENA ESCALA EM UM BAIRRO URBANO DE SALVADOR, BAHIA

O presente estudo teve como objetivo identificar áreas e esforço de pesca e recursos pesqueiros capturados pela frota linheira artesanal alocada no bairro da Pituba Salvador, Bahia - Brasil. Os dados foram coletados durante o ano de 2009 sendo monitorados 560 desembarques pesqueiros. Foram registradas no total 96 espécies sendo as de maior frequência de ocorrência (&gt; 15%) a bicuda (Sphyraena guachancho), ariacó (Lutjanus synagris), cavala (Scomberomorus cavalla), albacora (Thunnus atlanticus), bonito (Euthynus alleteratus), caçonete (Rhizoprionodon porosus) e dourado (Coryphaena hippurus). A dinâmica de pesca é sazonal marcada por entre safras do período chuvoso (março a agosto) e seco (setembro a março). Importante destacar que a área de pesca utilizada pela comunidade pesqueira é a mesma há mais de um século, sendo quantificada a utilização de 42 subáreas, se destacando a Lama (35,2%) dentre as mais visitadas principalmente no período chuvoso.

Trophic ecology of large pelagic fish in the Saint Peter and Saint Paul Archipelago, Brazil

Trophic relationships of large pelagic predators can determine the structure and dynamics of oceanic food webs. The feeding habits and trophic ecology of five large pelagic fish (Acanthocybium solandri, Coryphaena hippurus, Elagatis bipinnulata, Thunnus albacares and Thunnus atlanticus) in the Saint Peter and Saint Paul Archipelago were evaluated to determine whether there is a trophic-niche overlap or resource partitioning among them. Eighty prey items found in 1528 stomachs were identified and grouped into Cephalopoda, Cnidaria, Crustacea, Gastropoda, Teleostei and Tunicata. Exocoetidae and Scombridae were the main prey in the diet of Acanthocybium solandri. In C. hippurus, Cheilopogon cyanopterus and Exocoetus volitans were the most important prey items, whereas C. cyanopterus was the main prey for T. albacares. Thunnus atlanticus consumed a great proportion of invertebrate species, with shrimps of Sergestidae family being particularly important. The gastropod Cavolinia sp. was the most important prey for E. bipinnulata. The five species had a high trophic specialisation and a high trophic level (&amp;gt;4.4), whereas most dietary overlaps were consistently low. The most important factor for diet dissimilarity was the consumption of Exocoetidade. All species were classified as top predators with varied diets, indicating their structural and functional importance in the food web of the Archipelago.

Influence of oceanographic conditions on the distribution and abundance of blackfin tuna (Thunnus atlanticus) larvae in the Gulf of Mexico

Information on early life history of economical important fisheries stocks are required to accurately estimate their population status. This study investigated blackfin tuna (Thunnus atlanticus) larvae distribution over six summers (2007–2011, 2015) in the northern Gulf of Mexico. Blackfin tuna were commonly observed and widely distributed in surface waters with frequency of occurrence ranging from 48% (2008) to 92% (2011). Inter-annual variability in density was observed with highest mean density recorded in 2009 (17.2 larvae 1000 m−3) and lowest mean density in 2015 (2.2 larvae 1000 m−3). Density also varied between months with higher overall mean density observed in July (9.2 larvae 1000 m−3) compared to June (4.3 larvae 1000 m−3). Generalized additive models (GAMs) based on presence/absence and density of blackfin tuna larvae determined that this species was present in areas of intermediate salinity (31–36) and higher sea surface temperature (SST > 29 °C). Blackfin tuna larvae were also strongly associated with convergent zones near the Loop Current and anticyclonic eddies. Environmental conditions deemed to be favorable from GAMs (salinity, SST and sea surface height) were combined with environmental data in 2011 and 2015 to predict the suitable habitat of blackfin tuna larvae from the outer continental shelf into oceanic waters (areas ≥100 m isobath). The amount of highly suitable habitat ( >10 larvae 1000 m−3) in 2011 and 2015 varied between months (June 6%, July 51%); however, blackfin tuna larvae were predicted to occur at similar locations in surface waters along the continental slope and at the margin of the Loop Current. Overall, the results highlighted the importance of mesoscale features and oceanographic conditions on the distribution and abundance of blackfin tuna larvae.

Complete mitochondrial genome of the yellowfin tuna (Thunnus albacares) and the blackfin tuna (Thunnus atlanticus): notes on mtDNA introgression and paraphyly on tunas

The genus Thunnus is composed of eight species, which are separated into two groups, the temperate subgenus Thunnus (bluefin tunas group) and the tropical subgenus Neothunnus (yellowfin tunas group). We obtained the mitochondrial genome for two species from the yellowfin group, Thunnus albacares and Thunnus atlanticus, and compared to those from extant Thunnus species to reconstruct the mtDNA phylogenetic relationship within the genus. Our results coincide with previous studies using mtDNA and nuclear loci in the paraphyly of the bluefin group mainly as a result of the position of Thunnus obesus within the tree. Also, we support the introgression hypothesis of the mtDNA from albacore into Pacific Bluefin tuna.